From 1c8d0175df47364aa55c568b65ed7a3aee5b9a6d Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Wed, 2 May 2018 15:19:32 +0300 Subject: [PATCH] btrfs: Factor out read portion of btrfs_get_blocks_direct Currently this function handles both the READ and WRITE dio cases. This is facilitated by a bunch of 'if' statements, a goto short-circuit statement and a very perverse aliasing of "!created"(READ) case by setting lockstart = lockend and checking for lockstart < lockend for detecting the write. Let's simplify this mess by extracting the READ-only code into a separate __btrfs_get_block_direct_read function. This is only the first step, the next one will be to factor out the write side as well. The end goal will be to have the common locking/ unlocking code in btrfs_get_blocks_direct and then it will call either the read|write subvariants. No functional changes. Signed-off-by: Nikolay Borisov Signed-off-by: David Sterba --- fs/btrfs/inode.c | 56 +++++++++++++++++++++++++++++++++++++----------- 1 file changed, 43 insertions(+), 13 deletions(-) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index f81a48c47fe0..4f8fb1130cf3 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -7540,6 +7540,27 @@ static struct extent_map *create_io_em(struct inode *inode, u64 start, u64 len, return em; } + +static int btrfs_get_blocks_direct_read(struct extent_map *em, + struct buffer_head *bh_result, + struct inode *inode, + u64 start, u64 len) +{ + if (em->block_start == EXTENT_MAP_HOLE || + test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) + return -ENOENT; + + len = min(len, em->len - (start - em->start)); + + bh_result->b_blocknr = (em->block_start + (start - em->start)) >> + inode->i_blkbits; + bh_result->b_size = len; + bh_result->b_bdev = em->bdev; + set_buffer_mapped(bh_result); + + return 0; +} + static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create) { @@ -7608,11 +7629,29 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, goto unlock_err; } - /* Just a good old fashioned hole, return */ - if (!create && (em->block_start == EXTENT_MAP_HOLE || - test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) { + if (!create) { + ret = btrfs_get_blocks_direct_read(em, bh_result, inode, + start, len); + /* Can be negative only if we read from a hole */ + if (ret < 0) { + ret = 0; + free_extent_map(em); + goto unlock_err; + } + /* + * We need to unlock only the end area that we aren't using. + * The rest is going to be unlocked by the endio routine. + */ + lockstart = start + bh_result->b_size; + if (lockstart < lockend) { + clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, + lockend, unlock_bits, 1, 0, + &cached_state); + } else { + free_extent_state(cached_state); + } free_extent_map(em); - goto unlock_err; + return 0; } /* @@ -7624,12 +7663,6 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, * just use the extent. * */ - if (!create) { - len = min(len, em->len - (start - em->start)); - lockstart = start + len; - goto unlock; - } - if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags) || ((BTRFS_I(inode)->flags & BTRFS_INODE_NODATACOW) && em->block_start != EXTENT_MAP_HOLE)) { @@ -7716,10 +7749,7 @@ unlock: clear_extent_bit(&BTRFS_I(inode)->io_tree, lockstart, lockend, unlock_bits, 1, 0, &cached_state); - } else { - free_extent_state(cached_state); } - free_extent_map(em); return 0; -- 2.34.1